Len,

Park staff say that smallmouth are an underutilized resource in Opeongo, so it might be a productive way to spend time fishing for them. On a lake as large as Opeongo, trolling and covering distance could be the best way to find where they are... my bet is you'll catch some off of rocky points. Trolling a rapala, or a spinnerbait for fewer snags has worked.

Hailstorm creek gets a lot recs on internet sites and from outfitters, and if a more secluded place is what you're looking for, the nature reserve in the east arm at Slot lake has some old growth red pine stands and some small weedy lakes that may or may not be accessible with higher water. Also some interesting logging roads, both old and new, that I haven't checked out yet, they're on the list..... good luck.
 

Thanks Bo!!! Sproule is our "Plan B" i the fishing isn't good on Sunday Lake. 

Camped there 3 or 4 years ago.  
The Island site was pretty stripped of wood, we camped on the far east site and had a great western look over the water.  Lots of space for tents, firepit was against a large rock too   


 

Thanks to all for the help. Fishing was very slow but we didn't do too much of it. Highlight of the lake was 5 boisterous loons, and one particularly crazy one that kept on doing the breaststroke across the lake. There was also a dead moose in the lake that attracted a significant crowd of turkey vultures. Heard some barred owls at night and had one huge snapping turtle that was likely tamed by frequent campers. Sad to see but practically inevitable on busy lakes.